1. Field
The embodiments disclosed in this application relate to a memory system, and particularly to a memory system that includes a memory module on which a memory buffer is mounted, and a method of setting a mode of the memory module.
2. Description of Related Art
Semiconductor memory devices are used to store data in a variety of electronic products and applications. A memory module including a substrate and a plurality of semiconductor memory devices mounted on the substrate is typically used in electronic products, such as computers.
Recently, certain types of memory modules include a memory buffer for buffering a signal and data received from the exterior and to provide the signal and/or data to semiconductor memory devices mounted on the memory module. In a memory module on which semiconductor memory devices such as double data rate 3 (DDR3) are mounted, a function of mode register control is included in the memory buffer, and the memory module controls output signals of the memory buffer variously. For example, the mode register control signal (CMR) may control a magnitude or delay time of a signal.
In these systems, however, it is typically difficult for a memory module including semiconductor memory devices having a function of mode register control (CMR) to enter into certain other modes, such as a parallel test mode for a memory module that has a plurality of ranks.